Bio-electrode composition, bio-electrode, and method for manufacturing a bio-electrode

ABSTRACT

wherein R1 represents a linear, branched, or cyclic alkylene group having 1 to 20 carbon atoms optionally having an aromatic group, an ether group, or an ester group, or an arylene group having 6 to 10 carbon atoms; Rf represents a linear, branched, or cyclic alkyl group having 1 to 4 carbon atoms and containing at least one fluorine atom; M+ is an ion selected from a lithium ion, a sodium ion, a potassium ion, and a silver ion. This can form a living body contact layer for a bio-electrode that is excellent in electric conductivity and biocompatibility, light-weight, manufacturable at low cost, and free from large lowering of the electric conductivity even though it is wetted with water or dried.

TECHNICAL FIELD

The present invention relates to a bio-electrode that is used in contactwith the skin of a living body capable of detecting physical conditionssuch as heart rate by an electric signal transmitted from the skin, amethod for manufacturing the bio-electrode, and a bio-electrodecomposition desirably used for a bio-electrode.

BACKGROUND ART

A recent growing popularity of Internet of Things (IoT) has acceleratedthe development of such major wearable devices as watches and glassesthat allow for Internet access. Even in the fields of medicine andsports, wearable devices for constantly monitoring the user's physicalstate are increasingly demanded, and such technological development isexpected to be further encouraged.

In the field of medicine, including an electrocardiogram for detectingan electric signal to measure the motion of the heart, use of wearabledevices for monitoring the state of human organs by detecting extremelyweak current has been examined. The electrocardiogram measurement isconducted by attaching an electrode coated with an electro-conductivepaste to a body, but this is a single (not continuous), short-timemeasurement. On the other hand, the above medical wearable device isaimed at constantly monitoring the state of physical conditions for afew weeks. Accordingly, a bio-electrode used in a medical wearabledevice is required to make no changes in electric conductivity even inlong-time use and cause no skin allergy. In addition to these,bio-electrodes must be light-weight and produced at low cost.

Medical wearable devices are classified into two types: direct bodyattachment and clothing attachment. One typical body attachment deviceis a bio-electrode formed of a hydrophilic gel containing water andelectrolytes as ingredients of the above electro-conductive paste(Patent Document 1). The hydrophilic gel, containing sodium, potassium,and calcium electrolytes in a hydrophilic polymer containing water,detects changes in ion concentration from the skin to convert the datainto electricity. Meanwhile, one typical clothing attachment device ischaracterized by a method for using as an electrode a fabric includingan electro-conductive polymer, such as PEDOT-PSS(Poly-3,4-ethylenedioxythiophene-polystyrenesulfonate), and a silverpaste incorporated into the fiber (Patent Document 2).

However, the use of the hydrophilic gel containing water andelectrolytes unfortunately brings about loss of electric conductivitydue to water evaporation in drying process. Meanwhile, the use of ahigher ionization tendency metal such as copper can cause some users tosuffer from skin allergy. The use of an electro-conductive polymer suchas PEDOT-PSS can also cause skin allergy due to the strong acidity ofthe electro-conductive polymer, as well as peeling of theelectro-conductive polymer from fibers during washing.

By taking advantage of excellent electric conductivity, the use ofelectrode materials formed of metal nanowire, carbon black, or carbonnanotube has been examined (Patent Document 3, 4, and 5). With highercontact probability, metal nanowires can conduct electricity in smallquantities to be added. Nevertheless, metal nanowires, formed of apointed thin material, may cause skin allergy. Accordingly, even thoughthese electrode materials themselves cause no allergic reaction, thebiocompatibility can be degraded depending on the shape of a materialand its inherent stimulation, thereby failing to satisfy both electricconductivity and biocompatibility.

Although metal films seem to function as an excellent bio-electrodethanks to extremely high electric conductivity, this is not always thecase. Upon heartbeat, the human skin releases a sodium ion, a potassiumion, or a calcium ion, instead of extremely weak current. It is thusnecessary to convert changes in ion concentration into current, which iswhat less ionized precious metals unfortunately fail to do efficiently.The resulting bio-electrode including the precious metal ischaracterized by high impedance and high resistance to the skin duringelectrical conduction.

Meanwhile, the use of a battery containing an ionic liquid has beenexamined (Patent Document 6). Advantageously, the ionic liquid isthermally and chemically stable, and the electric conductivity isexcellent, providing more various battery applications. However, anionic liquid having smaller molecular weight shown in Patent Document 6unfortunately dissolves into water. A bio-electrode containing such anionic liquid in use allows the ionic liquid to be extracted from theelectrode by sweating, which not only lowers the electric conductivity,but also causes rough skin by the liquid soaking into the skin.

Batteries using a lithium salt of polymer type sulfonimide have beeninvestigated (Non-Patent Document 1). Lithium has been applied tobatteries because of their high ionic mobility, however, this is not amaterial with bio-compatibility. Additionally, lithium salts offluorosulfonate have been investigated in a form of a pendant onsilicone (Non-Patent Document 2).

The bio-electrode fails to give biological information when it is apartfrom the skin. The detection of even changes in contact area can varyquantities of electricity traveling through the electrode, allowing thebaseline of an electrocardiogram (electric signal) to fluctuate.Accordingly, in order to stably detect electric signals from the body,the bio-electrode is required to be in constant contact with the skinand make no changes in contact area. This requirement is satisfied,preferably by use of adhesive biomedical electrodes. Moreover, elasticand flexible biomedical electrodes are needed to follow changes in skinexpansion and flexion.

CITATION LIST Patent Literature

-   Patent Document 1: International Patent Laid-Open Publication No. WO    2013/039151-   Patent Document 2: Japanese Unexamined Patent Application    Publication No. 2015-100673-   Patent Document 3: Japanese Unexamined Patent Application    Publication No. H5-095924-   Patent Document 4: Japanese Unexamined Patent Application    Publication No. 2003-225217-   Patent Document 5: Japanese Unexamined Patent Application    Publication No. 2015-019806-   Patent Document 6: Japanese Unexamined Patent Application    Publication No. 2004-527902

Non Patent Literature

-   Non Patent Document 1: J. Mater. Chem. A, 2016, 4, p 10038-10069-   Non Patent Document 2: J. of the Electrochemical Society, 150(8),    A1090-A1094 (2003)

SUMMARY OF INVENTION Technical Problem

The present invention was made in view of the situation to solve theproblems, and has an object to provide a bio-electrode compositioncapable of forming a living body contact layer for a bio-electrode thatis excellent in electric conductivity and biocompatibility, islight-weight, can be manufactured at low cost, and can controlsignificant reduction in electric conductivity even though thebio-electrode is wetted with water or dried, a bio-electrode including aliving body contact layer formed of the bio-electrode composition, and amethod for manufacturing the bio-electrode.

Solution to Problem

To solve the above problems, the present invention provides abio-electrode composition comprising a silicone bonded to a sulfonimidesalt, wherein the sulfonimide salt is shown by the following generalformula (1):

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms or an arylene group having 6 to 10 carbonatoms, with the alkylene group optionally having an aromatic group, anether group, or an ester group; Rf represents a linear, branched, orcyclic alkyl group having 1 to 4 carbon atoms and containing at leastone fluorine atom; M⁺ is an ion selected from a lithium ion, a sodiumion, a potassium ion, and a silver ion.

The bio-electrode composition like this is capable of forming a livingbody contact layer for a bio-electrode that is excellent in electricconductivity and biocompatibility, light-weight, manufacturable at lowcost, and free from large lowering of the electric conductivity eventhough it is wetted with water or dried. In this description, thewording of “R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms, optionally having an ether group” includesan instance of the alkylene group that has an oxygen atom at theterminal (for example, —C₂H₄—O—SO₂—N⁻(M⁺)-SO₂Rf).

It is preferable that the silicone bonded to a sulfonimide salt have arepeating unit-a shown by the following general formula (2):

wherein R¹, Rf, and M⁺ are as defined above; R² represents a linear,branched, or cyclic alkyl group having 1 to 10 carbon atoms or an arylgroup having 6 to 10 carbon atoms, with the alkyl group optionallysubstituted by a halogen atom.

With the repeating unit-a like this, the bio-electrode composition isallowed to form a living body contact layer for a bio-electrode that isparticularly excellent in electric conductivity and biocompatibility,light-weight, manufacturable at low cost, and free from large loweringof the electric conductivity even though it is wetted with water ordried.

It is preferable that the inventive bio-electrode composition furthercomprise an adhesive resin as a component (B) in addition to thesilicone bonded to a sulfonimide salt as a component (A).

With both of the component (A) and the component (B) described above,the component (B) compatibilizes the component (A) to prevent elution ofthe salt, and the composition is allowed to improve the adhesion.

It is preferable that the component (B) be one or more resins selectedfrom a silicone resin, a (meth)acrylate resin, and a urethane resin.

With the component (B) like this, the bio-electrode composition is moresecurely prevented from elution of the component (A) and can be improvedin adhesion.

It is preferable that the component (B) contain a silicone resin havingan R_(x)SiO_((4-x)/2) unit (wherein, R represents a substituted orunsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms,and “x” is a number in a range of 2.5 to 3.5) and an SiO₂ unit,diorganosiloxane having an alkenyl group, and organohydrogenpolysiloxanehaving an SiH group.

With the component (B) like this, the bio-electrode composition is stillmore securely prevented from elution of the component (A) and can befurther improved in adhesion.

It is preferable that the inventive bio-electrode composition furthercomprise a carbon powder and/or a metal powder as a component (C).

This makes the cured material of the bio-electrode composition excellentin electric conductivity.

It is preferable that the carbon powder as the component (C) be eitheror both of carbon black and carbon nanotube.

This makes the bio-electrode composition particularly excellent inelectric conductivity.

It is preferable that the metal powder as the component (C) be a powderof a metal selected from gold, silver, platinum, copper, tin, titanium,nickel, aluminum, tungsten, molybdenum, ruthenium, chromium, and indium.It is more preferable that the metal powder be a silver powder, a copperpowder, a tin powder, or a titanium powder.

The component (C) like this makes it possible to further improve theelectronic conductivity of the inventive bio-electrode composition.Particularly, a silver powder is excellent in view of electricconductivity, cost, and biocompatibility.

It is preferable that the bio-electrode composition further comprise anorganic solvent as a component (D).

The bio-electrode composition like this is further improved in thecoating properties.

The present invention also provides a bio-electrode comprising anelectro-conductive base material and a living body contact layer formedon the electro-conductive base material;

wherein the living body contact layer is a cured material of thebio-electrode composition described above.

With the silicone bonded to a sulfonimide salt (sulfonimide saltsilicone), the inventive bio-electrode is allowed to achieve both ofelectric conductivity and biocompatibility, and is also allowed to haveadhesion, thereby making it possible to keep the contact area with skinconstant to obtain electric signals from skin stably with highsensitivity.

It is preferable that the electro-conductive base material comprise oneor more species selected from gold, silver, silver chloride, platinum,aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainlesssteel, chromium, titanium, carbon, and an electro-conductive polymer.

In the bio-electrode of the present invention, these electro-conductivebase materials can be used particularly favorably.

The present invention also provides a method for manufacturing abio-electrode having an electro-conductive base material and a livingbody contact layer formed on the electro-conductive base material,comprising:

applying the bio-electrode composition described above onto theelectro-conductive base material; and curing the bio-electrodecomposition; thereby forming the living body contact layer.

The inventive method for manufacturing a bio-electrode makes it possibleto manufacture the inventive bio-electrode, which is excellent inelectric conductivity and biocompatibility, light-weight, and free fromlarge lowering of the electric conductivity even though it is wettedwith water or dried, easily and at low cost.

It is preferable that the electro-conductive base material comprise oneor more species selected from gold, silver, silver chloride, platinum,aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainlesssteel, chromium, titanium, carbon, and an electro-conductive polymer.

In the inventive method for manufacturing a bio-electrode, theseelectro-conductive base materials can be used particularly favorably.

The present invention also provides a silicone compound comprising apartial structure shown by the following general formula (2):

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms or an arylene group having 6 to 10 carbonatoms, with the alkylene group optionally having an aromatic group, anether group, or an ester group; R² represents a linear, branched, orcyclic alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 10 carbon atoms, with the alkyl group optionally substituted by ahalogen atom; Rf represents a linear, branched, or cyclic alkyl grouphaving 1 to 4 carbon atoms and containing at least one fluorine atom; M⁺is an ion selected from a lithium ion, a sodium ion, a potassium ion,and a silver ion.

The silicone compound like this is useful as the component of abio-electrode composition to form a living body contact layer for abio-electrode that is capable of conducting electric signals from skinefficiently to a device (i.e., excellent in electric conductivity), freefrom the risk of causing allergies even when it is worn on skin for along time (i.e., excellent in biocompatibility), and free from largelowering of the electric conductivity even though it is wetted withwater or dried.

The present invention also provides a silicone polymer comprising arepeating unit shown by the following general formula (2), and having aweight average molecular weight in a range of 1000 to 1000000,

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms or an arylene group having 6 to 10 carbonatoms, with the alkylene group optionally having an aromatic group, anether group, or an ester group; R² represents a linear, branched, orcyclic alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 10 carbon atoms, with the alkyl group optionally substituted by ahalogen atom; Rf represents a linear, branched, or cyclic alkyl grouphaving 1 to 4 carbon atoms and containing at least one fluorine atom; M⁺is an ion selected from a lithium ion, a sodium ion, a potassium ion,and a silver ion.

The silicone polymer like this is particularly useful as the componentof a bio-electrode composition to form a living body contact layer for abio-electrode that is capable of conducting electric signals from skinefficiently to a device (i.e., excellent in electric conductivity), freefrom the risk of causing allergies even when it is worn on skin for along time (i.e., excellent in biocompatibility), and free from largelowering of the electric conductivity even though it is wetted withwater or dried.

Advantageous Effects of Invention

As described above, the inventive bio-electrode composition makes itpossible to form a living body contact layer for a bio-electrode that iscapable of conducting electric signals from skin efficiently to a device(i.e., excellent in electric conductivity), free from the risk ofcausing allergies even when it is worn on skin for a long time (i.e.,excellent in biocompatibility), light-weight, manufacturable at lowcost, and free from large lowering of the electric conductivity eventhough it is wetted with water or dried. The electric conductivity canbe further improved by adding an electro-conductive powder (carbonpowder, metal powder), and a bio-electrode can be produced withparticularly high adhesion and stretchability by combination of a resinthat has adhesion and stretchability. Additionally, the stretchabilityand the adhesion to skin can be improved using additives and can becontrolled by adjusting the composition of resin or the thickness ofliving body contact layer.

With the sulfonimide salt silicone described above, the inventivebio-electrode is allowed to achieve both of electric conductivity andbiocompatibility, and is also allowed to have adhesion, thereby makingit possible to keep the contact area with skin constant to obtainelectric signals from skin stably with high sensitivity.

Additionally, the inventive method for manufacturing a bio-electrodemakes it possible to manufacture the inventive bio-electrode, which isexcellent in electric conductivity and biocompatibility, light-weight,and free from large lowering of the electric conductivity even though itis wetted with water or dried, easily at low cost.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic sectional view showing an example of abio-electrode having a living body contact layer composed of a curedproduct of the inventive bio-electrode composition;

FIG. 2 is a schematic sectional view showing an example of the inventivebio-electrode worn on a living body;

FIG. 3A is a schematic view of the bio-electrode produced in Examples ofthe present invention viewed from the living body contact layer side;

FIG. 3B is a schematic view of the bio-electrode produced in Examples ofthe present invention viewed from the electro-conductive base materialside; and

FIG. 4 is a photograph of a scene of measuring impedance on the surfaceof skin by using the bio-electrode produced in Examples of the presentinvention.

DESCRIPTION OF EMBODIMENTS

As described above, it has been desired to develop a bio-electrodecomposition capable of forming a living body contact layer for abio-electrode that is excellent in electric conductivity andbiocompatibility, light-weight, manufacturable at low cost, and freefrom large lowering of the electric conductivity even though it iswetted with water or dried; a bio-electrode in which the living bodycontact layer is formed from the bio-electrode composition; and a methodfor manufacturing the same.

The surface of skin releases ions of sodium, potassium, and calcium inaccordance with heartbeat. The bio-electrode have to convert theincrease and decrease of these ions released from skin to electricsignals. Accordingly, the bio-electrode have to be composed of amaterial that is excellent in ionic conductivity to transmit theincrease and decrease of ions.

The present inventors have noticed ionic liquids as a material that ishighly ionic conductive. Ionic liquids are characterized by high thermaland chemical stability as well as excellent electric conductivity,thereby having been widely used for battery uses. Illustrative examplesof known ionic liquid include hydrochloric acid salt, hydrobromic acidsalt, hydroiodic acid salt, trifluoromethanesulfonic acid salt,nonafluorobutanesulfonic acid salt, bis(trifluoromethanesulfonyl)imideacid salt, hexafluorophosphate salt, and tetrafluoroborate salt ofsulfonium, phosphonium, ammonium, morpholinium, pyridinium,pyrrolidinium, and imidazolium. However, these salts (particularly, theones with low molecular weight) are generally liable to hydrate, therebycausing a defect such that the salt is extracted with perspiration or bywashing to lower the electric conductivity of a bio-electrode in whichthe living body contact layer is formed from a bio-electrode compositioncontaining these salts. In addition, the tetrafluoroborate salt ishighly toxic, and the other salts are highly water-soluble to easilypermeate into skin, thereby causing an issue of rough dry skin (i.e.,highly irritative to skin).

In neutralized salts formed from highly acidic acids, the ions arestrongly polarized to improve the ionic conductivity. This is the reasonwhy lithium salts of bis(trifluoromethanesulfonyl)imidic acid andtris(trifluoromethanesulfonyl)methide acid show high ionic conductivityas a lithium ion battery. On the other hand, the higher acidity makesthe salt have stronger irritation to a body. That is, ionic conductivityand irritation to a body are in relation of trade-off. In a salt appliedto a bio-electrode, however, higher ionic conductivity and lowerirritation to a body have to be combined.

The salt compound decreases the permeability and irritation to skin asthe molecular weight increases or the hydrophobicity increases.Accordingly, the salt compound bonded to silicone is ideal because ofthe large molecular weight and high hydrophobicity. Thus the presentinventors have conceived to synthesize a silicone compound bonded to anionic sulfonimide salt.

The present inventors have also conceived that the use of this saltmixed with adhesive (resin), such as a silicone type, an acrylic type,and a urethane type, makes it possible to achieve continuous adhesion toskin to obtain electric signals that are stable for a long time.

The inventors have diligently studied the above subjects and found thathigher ionic conductivity alone is inadequate to form a bio-electrodewith higher sensitivity, and higher electronic conductivity is alsonecessary in some cases; the electronic conductivity is improvedefficiently by adding particles (powders) of carbon or metal; thisallows the bio-electrode to function as a highly sensitive bio-electrodewith lower impedance; thereby bringing the present invention tocompletion.

That is, the present invention is a bio-electrode composition comprisinga silicone bonded to a sulfonimide salt, wherein the sulfonimide salt isshown by the following general formula (1):

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms or an arylene group having 6 to 10 carbonatoms, with the alkylene group optionally having an aromatic group, anether group, or an ester group; Rf represents a linear, branched, orcyclic alkyl group having 1 to 4 carbon atoms and containing at leastone fluorine atom; M⁺ is an ion selected from a lithium ion, a sodiumion, a potassium ion, and a silver ion.

Hereinafter, the present invention will be described specifically, butthe present invention is not limited thereto.

<Bio-Electrode Composition>

In the inventive bio-electrode composition, it is essential that asilicone bonded to a sulfonimide salt is contained, and the sulfonimidesalt is shown by the general formula (1). The bio-electrode compositionmay also contain both of the silicone bonded to a sulfonimide salt andan adhesive resin. The bio-electrode composition can also contain anelectro-conductive powder (carbon powder, metal powder) or an organicsolvent additionally.

Hereinafter, each component will be described more specifically.Incidentally, the following describes the silicone bonded to asulfonimide salt as “a component (A)”, an adhesive resin as “a component(B)”, an electro-conductive powder as “a component (C)”, and additivessuch as an organic solvent as “a component (D)”.

[Component (A)]

The inventive bio-electrode composition contains a component (A) (asilicone bonded to a sulfonimide salt) as an ionic material (salt). Theionic material (salt) added to the bio-electrode composition as anelectro-conductive material is a silicone compound bonded to a lithiumsalt, a sodium salt, a potassium salt, or a silver salt of sulfonimideshown by the general formula (1) described below. Incidentally, thesilicone bonded to a sulfonimide salt is also referred to as “asulfonimide salt silicone”.

The sulfonimide salt silicone is a silicone compound having a chemicalstructure in which a partial structure composed of a sulfonimide salt isbonded to a silicone chain. The lithium salt, sodium salt, potassiumsalt, and silver salt of sulfonimide of the partial structure is shownby the following general formula (1):

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms that may have an aromatic group, an ethergroup, or an ester group, or an arylene group having 6 to 10 carbonatoms; Rf represents a linear, branched, or cyclic alkyl group having 1to 4 carbon atoms and containing at least one fluorine atom; M⁺ is anion selected from a lithium ion, a sodium ion, a potassium ion, and asilver ion.

The silicone bonded to a sulfonimide salt preferably has a repeatingunit-a shown by the following general formula (2):

wherein R¹, Rf, and M⁺ are as defined above; R² represents a linear,branched, or cyclic alkyl group having 1 to 10 carbon atoms that may besubstituted by a halogen atom, or an aryl group having 6 to 10 carbonatoms.

As the repeating unit-a shown by the general formula (2), the followingones can be exemplified specifically.

Hereinabove, M⁺ is as defined above.

(Repeating Unit-b)

The component (A) of the inventive bio-electrode composition may containa repeating unit-b composed of siloxane having a glyme chain in additionto the repeating unit-a in order to improve the electric conductivity.As the repeating unit-b, the following ones can be exemplifiedspecifically.

In the formulae, 0≥m≥20, 0≥n≥20, and 1≤m+n≤20.

(Repeating Unit-c)

The component (A) of the inventive bio-electrode composition may containa repeating unit-c composed of siloxane having a hydrogen atom, an alkylgroup, and/or an aryl group in addition to the repeating units-a and/or-b in order to improve the mixing property with the adhesive resin ofthe component (B). The alkyl group and the aryl group may contain ahydroxy group, a halogen atom, an ester group, an ether group, a carboxygroup, a thiol group, a (meth)acryl group, a cyano group, and/or a nitrogroup. As the repeating unit-c, the following ones can be exemplifiedspecifically.

As a method for synthesizing the silicone compound having the repeatingunit-a (a-unit) of the component (A) (sulfonimide salt silicone), amethod by hydrosilylation reaction is exemplified. The silicone compoundcan be obtained by hydrosilylation reaction of a sulfonimide salt havinga double bond and a silicone compound having an Si—H group under aplatinum catalyst. The repeating unit-b (b-unit) having a glyme chaincan be obtained by hydrosilylation reaction of a compound having adouble bond and an ether group, together with a silicone compound havingan Si—H group, under a platinum catalyst. The a-unit and the b-unit maybe contained in the same silicone molecule or may be prepared byblending silicone compounds each having the a-unit or the b-unit. Theformer example includes a copolymer of the a-unit and the b-unit. In thecopolymer of the a-unit and the b-unit, the copolymerization ratio issuch that 0<a<1.0 and 0<b≤a<1.0.

The silicone compound bonded to a sulfonimide salt is preferablysynthesized by mixing a sulfonimide salt having a double bond, an ethercompound having a double bond in accordance with needs, a siliconecompound having an SiH group, and a platinum catalyst, followed byheating to promote the hydrosilylation reaction.

The silicone compound having an Si—H group may be any of a linear form,a branched form, and a cyclic form before the hydrosilylation, but ispreferably a polymer compound with a weight average molecular weight of1000 or more and 1000000 or less. The use of such a silicone compoundhaving an Si—H group makes it possible to synthesis a polymer ofsulfonimide salt silicone with a weight average molecular weight of 1000to 1000000.

As described above, the addition of a sulfonimide salt as a pendant to asilicone polymer makes the salt compound have larger molecular weightand higher hydrophobicity. In general, the salt compound decreases thepermeability to skin to decrease irritation to skin as the molecularweight increases or the hydrophobicity increases. Accordingly, such apolymer compound can be more securely prevented from permeating to skinto cause allergies.

As described above, it is possible to synthesize a silicone compoundhaving a partial structure shown by the general formula (2) (sulfonimidesalt silicone) or a silicone polymer with a weight average molecularweight of 1000 to 1000000 having the repeating unit shown by the generalformula (2). Each of the silicone compound and the silicone polymerdescribed above is suitable as an ionic material (salt) to be blended tothe inventive bio-electrode composition as an electro-conductivematerial.

In the inventive bio-electrode composition, the amount of the component(A) is preferably 0.1 to 300 parts by mass, more preferably 1 to 200parts by mass on the basis of 100 parts by mass of the component (B).The component (A) may be used singly or in admixture of two or morekinds.

[Component (B)]

The inventive bio-electrode composition can contain an adhesive resin asthe component (B) in addition to the component (A). The component (B)contained in the bio-electrode composition is a component forcompatibilizing (A) the sulfonimide salt silicone to prevent elution ofthe salt, for holding an electric conductivity improver such as carbonpowders and/or metal powders, and for achieving adhesion; and iscomposed of an adherent resin. It is to be noted that the component (B)may be any of a resin other than the component (A) and is preferablyeither or both of a thermosetting resin and a photo-curable resin,particularly one or more resins selected from silicone resins (siliconebase resins), (meth)acrylate resins (acrylic base resins), and urethaneresins (urethane base resins).

The adherent silicone base resin include an addition-curable (additionreaction-curable) type and a radical curable (radical crosslinkingreaction-curable) type. As the addition-curable type, it is possible touse one that contains diorganosiloxane having an alkenyl group(s), an MQresin having an R₃SiO_(0.5) unit and an SiO₂ unit,organohydrogenpolysiloxane having a plurality of SiH groups, a platinumcatalyst, an addition reaction inhibitor, and an organic solvent, forexample, described in JP 2015-193803A. As the radical curable type, itis possible to use one that contains diorganopolysiloxane with orwithout an alkenyl group, an MQ resin having an R₃SiO_(0.5) unit and anSiO₂ unit, organic peroxide, and an organic solvent, for example,described in JP 2015-193803A. Herein, R represents a substituted orunsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms.

It is also possible to use a polysiloxane-resin integrated compound thatis formed by condensation reaction of an MQ resin and polysiloxanehaving silanol at the terminal or the side chain of the polymer. The MQresin contains many silanol and improves adhesion by addition of it, butdoes not bind to polysiloxane in molecular level because it is notcrosslinkable. The adhesion can be increased by integrating thepolysiloxane and the resin as described above.

The silicone resin may contain modified siloxane that has a groupselected from an amino group, an oxirane group, an oxetane group, apolyether group, a hydroxy group, a carboxy group, a mercapto group, amethacryl group, an acryl group, a phenol group, a silanol group, acarboxylic anhydride group, an aryl group, an aralkyl group, an amidegroup, an ester group, and a lactone ring. The addition of modifiedsiloxane improves dispersibility of the component (A) in the siliconeresin. The modified siloxane may be modified at any part such as the oneterminal, the both terminals, or the side chain of the siloxane.

As the adherent acrylic base resin, it is possible to use one havinghydrophilic (meth)acrylic ester and hydrophobic long chain (meth)acrylicester as the repeating units described in JP 2016-011338A, for example.In some cases, it is also possible to copolymerize (meth)acrylic esterhaving a functional group or (meth)acrylic ester having a siloxane bond.

As the adherent urethane base resin, it is possible to use one having aurethane bond with a polyether bond, a polyester bond, a polycarbonatebond, or a siloxane bond described in JP 2016-065238A, for example.

In the inventive bio-electrode composition, the component (B) preferablyhas high compatibility with the component (A) to prevent lowering of theelectric conductivity due to elution of the component (A) from theliving body contact layer. In the inventive bio-electrode composition,the component (B) is preferably highly adhesive to theelectro-conductive base material to prevent peeling of the living bodycontact layer from the electro-conductive base material. In order toincrease the compatibility of the resin with the electro-conductive basematerial and the salt, the use of a resin with high polarity iseffective. Illustrative examples of such a resin include resin havingone or more moieties selected from an ether bond, an ester bond, anamide bond, an imide bond, a urethane bond, a thiourethane bond, and athiol group, such as a polyacrylic resin, a polyamide resin, a polyimideresin, a polyurethane resin, and a polythiourethane resin. On the otherhand, the living body contact layer is in contact with a living body,thereby being susceptible to perspiration. Accordingly, in the inventivebio-electrode composition, the component (B) preferably has highrepellency, and is hardly hydrolyzed. To make the resin be highlyrepellent and hardly hydrolyzed, the use of a silicon-containing resinis effective.

The silicon atom-containing polyacrylic resin includes a polymer thathas a silicone main chain and a polymer that has a silicon atom(s) onthe side chain, each of which can be suitably used. As the polymer thathas a silicone main chain, silsesquioxane or siloxane having a(meth)acrylpropyl group and so on can be used. In this case, an additionof a photoradical generator allows the (meth)acryl moiety to polymerizeto cure.

As the silicon atom-containing polyamide resin, it is possible tosuitably use polyamide silicone resins described in JP 2011-079946A andU.S. Pat. No. 5,981,680, for example. Such a polyamide silicone resincan be synthesized by combining a silicone or non-silicone compoundhaving amino groups at the both terminals and a non-silicone or siliconecompound having carboxy groups at the both terminals.

It is also possible to use polyamic acid before cyclization thereof,which is obtained by reacting carboxylic anhydride and amine. Thecarboxy group of the polyamic acid may be crosslinked by using acrosslinking agent such as an epoxy type and an oxetane type. It is alsopossible to esterify the carboxy group with hydroxyethyl (meth)acrylateto perform photoradical crosslinking of the (meth)acrylate moiety.

As the silicon atom-containing polyimide resin, it is possible tosuitably use polyimide silicone resins described in JP 2002-332305A, forexample. Although polyimide resins have very high viscosity, theviscosity can be decreased by blending a (meth)acrylic monomer as asolvent and a crosslinking agent.

Illustrative examples of the silicon atom-containing polyurethane resininclude polyurethane silicone resins. These polyurethane silicone resinscan be crosslinked through urethane bond by blending a compound havingisocyanate groups at the both terminals and a compound having a hydroxygroup(s) at the terminal(s), followed by heating thereof. In this case,a silicon atom(s) (siloxane bond) have to be contained in either or bothof the compound having isocyanate groups at the both terminals and thecompound having a hydroxy group(s) at the terminal(s). Alternatively, aurethane (meth)acrylate monomer and polysiloxane can be blended andphoto-crosslinked as described in JP 2005-320418A. It is also possibleto photo-crosslink a polymer having both of a siloxane bond(s) and aurethane bond(s), with the terminal having a (meth)acrylate group(s).

The silicon atom-containing polythiourethane resin can be obtained byreaction of a compound having a thiol group(s) and a compound having anisocyanate group(s), provided that either of them have to contain asilicon atom(s). It can also be photo-cured if (meth)acrylate groups arecontained at the terminals.

The silicone base resin is improved in compatibility with the foregoingsalt by adding modified siloxane that has a group selected from an aminogroup, an oxirane group, an oxetane group, a polyether group, a hydroxygroup, a carboxy group, a mercapto group, a methacryl group, an acrylgroup, a phenol group, a silanol group, a carboxylic anhydride group, anaryl group, an aralkyl group, an amide group, an ester group, and alactone ring in addition to the diorganosiloxane having an alkenylgroup(s), the MQ resin having an R₃SiO_(0.5) unit and an SiO₂ unit, andthe organohydrogenpolysiloxane having a plurality of SiH groups.

As will be described later, the living body contact layer is a curedmaterial of the bio-electrode composition. Curing the same improves theadhesion of the living body contact layer to both of skin and theelectro-conductive base material. The curing means is not limited, andcommon means can be used, including crosslinking reaction by either orboth of heat and light, an acid catalyst, or a base catalyst. Thecrosslinking reaction can be performed by appropriately selecting acrosslinking method described in “Kakyou han-nou handbook (handbook ofcrosslinking reaction)”, Chapter 2, pages 51-371, Yasuharu Nakamura,Maruzen shuppan (2013).

The diorganosiloxane having an alkenyl group(s) andorganohydrogenpolysiloxane having a plurality of SiH groups can becrosslinked through an addition reaction with a platinum catalyst.

Illustrative examples of the platinum catalyst include platinum-basedcatalysts such as platinic chloride, alcohol solution of platinicchloride, reaction product of platinic chloride and alcohol, reactionproduct of platinic chloride and an olefin compound, reaction product ofplatinic chloride and vinyl group-containing siloxane, a platinum-olefincomplex, a complex of platinum and vinyl group-containing siloxane;platinum group metal-based catalysts such as a rhodium complex and aruthenium complex. These catalysts may be used after dissolved ordispersed in alcohol solvent, hydrocarbon solvent, or siloxane solvent.

The amount of platinum catalyst is preferably in a range of 5 to 2,000ppm, particularly in a range of 10 to 500 ppm on the basis of 100 partsby mass of the resin.

When the addition curable silicone resin is used, an addition reactioninhibitor may be added. This addition reaction inhibitor is added as aquencher to prevent the platinum catalyst from acting in the solvent orunder a low temperature circumstance after forming the coating film andbefore heat curing. Illustrative examples thereof include3-methyl-1-butyn-3-ol, 3-methyl-1-pentyn-3-ol,3,5-dimethyl-1-hexyn-3-ol, 1-ethynylcyclohexanol,3-methyl-3-trimethylsiloxy-1-butyne,3-methyl-3-trimethylsiloxy-1-pentyne,3,5-dimethyl-3-trimethylsiloxy-1-hexyne,1-ethynyl-1-trimethylsiloxycyclohexane,bis(2,2-dimethyl-3-butynoxy)dimethylsilane,1,3,5,7-tetramethyl-1,3,5,7-tetravinylcyclotetrasiloxane, and1,1,3,3-tetramethyl-1,3-divinyldisiloxane.

The amount of addition reaction inhibitor is preferably in a range of 0to 10 parts by mass, particularly in a range of 0.05 to 3 parts by masson the basis of 100 parts by mass of the resin.

Illustrative examples of photo-curing method include a method of addinga photoradical generator to generate radical by light, together withusing a resin having a (meth)acrylate terminal(s) or an olefinterminal(s) or adding a crosslinking agent with the terminal(s) being(meth)acrylate, olefin, or a thiol group(s); and a method of adding aphoto-acid generator to generate acid by light, together with using aresin or a crosslinking agent having an oxirane group(s), an oxetanegroup(s), or a vinyl ether group(s).

Illustrative examples of the photoradical generator includeacetophenone, 4,4′-dimethoxybenzyl, benzyl, benzoin, benzophenone,2-benzoylbenzoic acid, 4,4′-bis(dimethylamino)benzophenone,4,4′-bis(diethylamino)benzophenone, benzoin methyl ether, benzoin ethylether, benzoin isopropyl ether, benzoin butyl ether, benzoin isobutylether, 4-benzoylbenzoic acid,2,2′-bis(2-chlorophenyl)-4,4′,5,5′-tetraphenyl-1,2′-biimidazole, methyl2-benzoylbenzoic acid,2-(1,3-benzodioxole-5-yl)-4,6-bis(trichloromethyl)-1,3,5-triazine,2-benzyl-2-(dimethylamino)-4′-morpholinobutyrophenone,4,4′-dichlorobenzophenone, 2,2-diethoxyacetophenone,2,2-dimethoxy-2-phenylacetophenone, 2,4-diethylthioxanthene-9-one,diphenyl(2,4,6-trimethylbenzoyl)phosphine oxide (BAPO),1,4-dibenzoylbenzene, 2-ethylanthraquinone, 1-hydroxycyclohexyl phenylketone, 2-hydroxy-2-methylpropiophenone,2-hydroxy-4′-(2-hydroxyethoxy)-2-methylpropiophenone,2-isonitrosopropiophenone, and2-phenyl-2-(p-toluenesulfonyloxy)acetophenone.

The curing can also be performed by adding a radical generator of a heatdecomposition type. Illustrative examples of the thermal radicalgenerator include 2,2′-azobis(isobutyronitrile),2,2′-azobis(2,4-dimethylvaleronitrile),2,2′-azobis(2-methylbutyronitrile), 2,2′-azobis(methylpropionamidine)hydrochloride, 2,2′-azobis[2-(2-imidazolin-2-yl)propane] hydrochloride,2,2′-azobis(4-methoxy-2,4-dimethylvaleronitrile),2,2′-azobis(cyclohexane-1-carbonitrile),1[(1-cyano-1-methylethyl)azo]formamide,2,2′-azobis[2-methyl-N-(2-hydroxyethyl)propionamide],2,2′-azobis[N-(2-propenyl)-2-methylpropionamide],2,2′-azobis(N-butyl-2-methylpropionamide),dimethyl-2,2′-azobis(isobutylate), 4,4′-azobis(4-cyanopentanoic acid),dimethyl-2,2′-azobis(2-methylpropionate), benzoyl peroxide, tert-butylhydroperoxide, cumene hydroperoxide, di-tert-butyl peroxide,di-tert-amyl peroxide, di-n-butyl peroxide, and dicumyl peroxide.

Illustrative examples of the photo-acid generator include sulfoniumsalt, iodonium salt, sulfonyldiazomethane, N-sulfonyloxyimide, andoxime-O-sulfonate type acid generators. Specific examples of thephoto-acid generator is described in paragraphs [0122] to [0142] of JP2008-111103A, together with JP 2009-080474A.

The amount of radical generator or photo-acid generator is preferably ina range of 0.1 to 50 parts by mass on the basis of 100 parts by mass ofthe resin.

Among them, particularly preferable resin of the component (B) containsa silicone resin having an R_(x)SiO_((4-x)/2) unit (wherein, Rrepresents a substituted or unsubstituted monovalent hydrocarbon grouphaving 1 to 10 carbon atoms, and “x” is a number in a range of 2.5 to3.5) and an SiO₂ unit, diorganosiloxane having an alkenyl group, andorganohydrogenpolysiloxane having an SiH group.

[Component (C)]

The inventive bio-electrode composition can further contain anelectro-conductive powder as the component (C). The electro-conductivepowder may be any powder having electric conductivity and is notparticularly limited, but a carbon powder (carbon material) and a metalpowder are preferable. The inventive bio-electrode composition containsthe component (A) (silicone bonded to a sulfonimide salt) as an ionicmaterial (salt) and can be further improved in electric conductivity byadding these electro-conductive powders (carbon powder, metal powder).Incidentally, the electro-conductive powder is also referred to as “anelectric conductivity improver” in the following.

[Carbon Powder]

As the electric conductivity improver, a carbon material (carbon powder)can be added. The carbon material may be exemplified by carbon black,carbon nanotube, carbon fiber, and the like. The carbon nanotube may beeither single layer or multilayer, and the surface may be modified withan organic group(s). The amount of carbon material is preferably in arange of 1 to 50 parts by mass on the basis of 100 parts by mass of theresin.

[Metal Powder]

The inventive bio-electrode composition preferably contains a metalpowder selected from gold, silver, platinum, copper, tin, titanium,nickel, aluminum, tungsten, molybdenum, ruthenium, chromium, and indiumas the component (C) in order to improve electronic conductivity. Theamount of the metal powder is preferably in a range of 1 to 50 parts bymass on the basis of 100 parts by mass of the resin.

As the kind of the metal powder, gold, silver, and platinum arepreferable in view of electric conductivity; and silver, copper, tin,titanium, nickel, aluminum, tungsten, molybdenum, ruthenium, andchromium are preferable in view of cost. In view of biocompatibility,noble metals are preferable. On the whole of these viewpoints, silver,copper, tin, and titanium are most preferable.

The metal powder may have any shape, such as a spherical shape, a diskshape, a flaky shape, and a needle shape. The addition of flaky powderbrings highest electric conductivity and is preferable thereby. Themetal powder is preferably a flake having relatively lower density andlarger specific surface area with a size of 100 μm or less, a tappeddensity of 5 g/cm³ or less, and a specific surface area of 0.5 m²/g ormore. It is also possible to add both of the metal powder and the carbonmaterial (carbon powder) as the electric conductivity improver.

[Component (D)]

The inventive bio-electrode composition can further contain anadditive(s) as a component (D) in accordance with needs. The additivemay be any material other than the components (A) to (C) and is notparticularly limited. Illustrative examples thereof include a componentthat can improve the stretchability or adhesion of a cured material ofthe bio-electrode composition, such as a tackifier; a component topromote the curing reaction, such as a radical generator and a platinumcatalyst; and a component to facilitate the handling of a bio-electrodecomposition, such as an organic solvent. Hereinafter, the component (D)will be described specifically.

[Tackifier]

The inventive bio-electrode composition may contain a tackifier in orderto have adhesion to a living body. Illustrative examples of such atackifier include silicone resin, as well as non-crosslinkable siloxane,non-crosslinkable poly(meth)acrylate, and non-crosslinkable polyether.The inventive bio-electrode composition can contain an adhesive resin asthe component (B) in accordance with needs and has more preferableadhesion to a living body by adding the tackifier like this.

[Organic Solvent]

The inventive bio-electrode composition may contain an organic solvent.Illustrative examples of the organic solvent include aromatichydrocarbon solvent such as toluene, xylene, cumene,1,2,3-trimethylbenzene, 1,2,4-trimethylbenzene, 1,3,5-trimethylbenzene,styrene, α-methylstyrene, butylbenzene, sec-butylbenzene,isobutylbenzene, cymene, diethylbenzene, 2-ethyl-p-xylene,2-propyltoluene, 3-propyltoluene, 4-propyltoluene,1,2,3,5-tetramethyltoluene, 1,2,4,5-tetramethyltoluene,tetrahydronaphthalene, 4-phenyl-1-butene, tert-amylbenzene, amylbenzene,2-tert-butyltoluene, 3-tert-butyltoluene, 4-tert-butyltoluene,5-isopropyl-m-xylene, 3-methylethylbenzene, tert-butyl-3-ethylbenzene,4-tert-butyl-o-xylene, 5-tert-butyl-m-xylene, tert-butyl-p-xylene,1,2-diisopropylbenzene, 1,3-diisopropylbenzene, 1,4-diisopropylbenzene,dipropylbenzene, pentamethylbenzene, hexamethylbenzene, hexylbenzene,and 1,3,5-triethylbenzene; aliphatic hydrocarbon solvent such asn-heptane, isoheptane, 3-methylhexane, 2,3-dimethylpentane,3-ethylpentane, 1,6-heptadiene, 5-methyl-1-hexyn, norbornane,norbornene, dicyclopentadiene, 1-methyl-1,4-cyclohexadiene, 1-heptyne,2-heptyne, cycloheptane, cycloheptene, 1,3-dimethylcyclopentane,ethylcyclopentane, methylcyclohexane, 1-methyl-1-cyclohexene,3-methyl-1-cyclohexene, methylenecyclohexane, 4-methyl-1-cyclohexene,2-methyl-1-hexene, 2-methyl-2-hexene, 1-heptene, 2-heptene, 3-heptene,n-octane, 2,2-dimethylhexane, 2,3-dimethylhexane, 2,4-dimethylhexane,2,5-dimethylhexane, 3,3-dimethylhexane, 3,4-dimethylhexane,3-ethyl-2-methylpentane, 3-ethyl-3-methylpentane, 2-methylheptane,3-methylheptane, 4-methylheptane, 2,2,3-trimethylpentane,2,2,4-trimethylpentane, cyclooctane, cyclooctene,1,2-dimethylcyclohexane, 1,3-dimethylcyclohexane,1,4-dimethylcyclohexane, ethylcyclohexane, vinylcyclohexane,isopropylcyclopentane, 2,2-dimethyl-3-hexene, 2,4-dimethyl-1-hexene,2,5-dimethyl-1-hexene, 2,5-dimethyl-2-hexene, 3,3-dimethyl-1-hexene,3,4-dimethyl-1-hexene, 4,4-dimethyl-1-hexene, 2-ethyl-1-hexene,2-methyl-1-heptene, 1-octene, 2-octene, 3-octene, 4-octene,1,7-octadiene, 1-octyne, 2-octyne, 3-octyne, 4-octyne, n-nonane,2,3-dimethylheptane, 2,4-dimethylheptane, 2,5-dimethylheptane,3,3-dimethylheptane, 3,4-dimethylheptane, 3,5-dimethylheptane,4-ethylheptane, 2-methyloctane, 3-methyloctane, 4-methyloctane,2,2,4,4-tetramethylpentane, 2,2,4-trimethylhexane,2,2,5-trimethylhexane, 2,2-dimethyl-3-heptene, 2,3-dimethyl-3-heptene,2,4-dimethyl-1-heptene, 2,6-dimethyl-1-heptene, 2,6-dimethyl-3-heptene,3,5-dimethyl-3-heptene, 2,4,4-trimethyl-1-hexene,3,5,5-trimethyl-1-hexene, 1-ethyl-2-methylcyclohexane,1-ethyl-3-methylcyclohexane, 1-ethyl-4-methylcyclohexane,propylcyclohexane, isopropylcylohexane, 1,1,3-trimethylcyclohexane,1,1,4-trimethylcyclohexane, 1,2,3-trimethylcyclohexane,1,2,4-trimethylcyclohexane, 1,3,5-trimethylcyclohexane,allylcyclohexane, hydrindane, 1,8-nonadiene, 1-nonyne, 2-nonyne,3-nonyne, 4-nonyne, 1-nonene, 2-nonene, 3-nonene, 4-nonene, n-decane,3,3-dimethyloctane, 3,5-dimethyloctane, 4,4-dimethyloctane,3-ethyl-3-methylheptane, 2-methylnonane, 3-methylnonane, 4-methylnonane,tert-butylcyclohexane, butylcyclohexane, isobutylcyclohexane,4-isopropyl-1-methylcyclohexane, pentylcyclopentane,1,1,3,5-tetramethylcyclohexane, cyclododecane, 1-decene, 2-decene,3-decene, 4-decene, 5-decene, 1,9-decadiene, decahydronaphthalene,1-decyne, 2-decyne, 3-decyne, 4-decyne, 5-decyne, 1,5,9-decatriene,2,6-dimethyl-2,4,6-octatriene, limonene, myrcene,1,2,3,4,5-pentamethylcyclopentadiene, α-phellandrene, pinene, terpinene,tetrahydrodicyclopentadiene, 5,6-dihydrodicyclopentadiene,1,4-decadiyne, 1,5-decadiyne, 1,9-decadiyne, 2,8-decadiyne,4,6-decadiyne, n-undecane, amylcyclohexane, 1-undecene,1,10-undecadiene, 1-undecyne, 3-undecyne, 5-undecyne,tricyclo[6.2.1.0^(2,7)]undeca-4-ene, n-dodecane, 2-methylundecane,3-methylundecane, 4-methylundecane, 5-methylundecane,2,2,4,6,6-pentamethylheptane, 1,3-dimethyladamantane, 1-ethyladamantane,1,5,9-cyclododecatriene, 1,2,4-trivinylcyclohexane, and isoparaffin;ketone solvent such as cyclohexanone, cyclopentanone, 2-octanone,2-nonanone, 2-heptanone, 3-heptanone, 4-heptanone, 2-hexanone,3-hexanone, diisobutyl ketone, methylcyclohexanone, and methyl n-pentylketone; alcohol solvent such as 3-methoxybutanol,3-methyl-3-methoxybutanol, 1-methoxy-2-propanol, and1-ethoxy-2-propanol; ether solvent such as propylene glycol monomethylether, ethylene glycol monomethyl ether, propylene glycol monoethylether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether,diethylene glycol dimethyl ether, diisopropyl ether, diisobutyl ether,diisopentyl ether, di-n-pentyl ether, methyl cyclopentyl ether, methylcyclohexyl ether, di-n-butyl ether, di-sec-butyl ether, di-sec-pentylether, di-tert-amyl ether, di-n-hexyl ether, and anisole; ester solventsuch as propylene glycol monomethyl ether acetate, propylene glycolmonoethyl ether acetate, ethyl lactate, ethyl pyruvate, butyl acetate,methyl 3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butylacetate, tert-butyl propionate, propylene glycol mono-tert-butyl etheracetate; lactone solvent such as γ-butyrolactone.

The amount of organic solvent is preferably in a range of 10 to 50,000parts by mass on the basis of 100 parts by mass of the resin. Theinventive bio-electrode composition is more improved in coating propertyby containing an organic solvent as the component (D).

As described above, the inventive bio-electrode composition makes itpossible to form a living body contact layer for a bio-electrode that iscapable of conducting electric signals from skin efficiently to a device(i.e., excellent in electric conductivity), free from the risk ofcausing allergies even when it is worn on skin for a long time (i.e.,excellent in biocompatibility), light-weight, manufacturable at lowcost, and free from large lowering of the electric conductivity eventhough it is wetted with water or dried. It is possible to improve theelectric conductivity still more by adding an electro-conductive powder(carbon powder, metal powder), and to manufacture a bio-electrode withparticularly high adhesion and stretchability by combining a resin withadhesion and stretchability. Furthermore, it is possible to improve thestretchability and adhesion to skin using additives, and to control thestretchability and adhesion by adjusting the composition of the resinand the thickness of the living body contact layer appropriately.

<Bio-Electrode>

The present invention also provides a bio-electrode comprising anelectro-conductive base material and a living body contact layer formedon the electro-conductive base material; wherein the living body contactlayer is a cured material of the inventive bio-electrode compositiondescribed above.

Hereinafter, the inventive bio-electrode will be specifically describedby reference to the FIGS., but the present invention is not limitedthereto.

FIG. 1 is a schematic sectional view showing an example of the inventivebio-electrode. The bio-electrode 1 of FIG. 1 has the electro-conductivebase material 2 and the living body contact layer 3 formed on theelectro-conductive base material 2. The living body contact layer 3 iscomposed of a cured material of the inventive bio-electrode composition.The ionic silicone material 4 composing the living body contact layer 3contains a cured material of the sulfonimide salt silicone. The livingbody contact layer 3 can also contain the resin 6 other than the ionicsilicone material 4 and/or an electro-conductive powder (the metalpowder 5 a, the carbon powder 5 b; hereinafter, they are also referredto as a general term of “the electro-conductive powder 5”). Hereinafter,the living body contact layer 3 is described as a layer in which theionic silicone material 4 and the electro-conductive powder 5 aredispersed in the resin 6 by referring FIGS. 1 and 2, but the inventivebio-electrode is not limited to this embodiment. Incidentally, 5 b inthe figures represents carbon nanotube.

In using the bio-electrode 1 of FIG. 1 like this, electric signals arepicked from the living body 7 through the ionic silicone material 4 andthe electro-conductive powder 5 while bringing the living body contactlayer 3 (i.e., the layer in which the ionic silicone material 4 and theelectro-conductive powder 5 are dispersed in the resin 6) into contactwith the living body 7, and then conducted to a sensor device (notshown) through the electro-conductive base material 2 as shown in FIG.2. As described above, the inventive bio-electrode is capable of copingwith both electric conductivity and biocompatibility by using the ionicsilicone material described above and obtaining electric signals fromskin stably in high sensitivity because the contact area with skin iskept constant due to the adhesion thereof.

Hereinafter, each component composing the inventive bio-electrode willbe described more specifically.

[Electro-Conductive Base Material]

The inventive bio-electrode comprises an electro-conductive basematerial. This electro-conductive base material is usually connectedelectrically with a sensor device and so on, and conducts electricalsignals picked from a living body through the living body contact layerto the sensor device and so on.

As the electro-conductive base material, any electro-conductive materialcan be used without being limited to particular ones. However, it ispreferable to comprise one or more species selected from gold, silver,silver chloride, platinum, aluminum, magnesium, tin, tungsten, iron,copper, nickel, stainless steel, chromium, titanium, carbon, and anelectro-conductive polymer, for example.

The electro-conductive base material may be a hard electro-conductivesubstrate, an electro-conductive film having flexibility, a cloth withthe surface being coated with electro-conductive paste, or a cloth intowhich electro-conductive polymer is kneaded without being limited toparticular substrates. The electro-conductive base material may be flat,uneven, or mesh-form of woven metal wires, which can be appropriatelyselected in accordance with the use of the bio-electrode.

[Living Body Contact Layer]

The inventive bio-electrode comprises a living body contact layer formedon the electro-conductive base material. This living body contact layeris a part to be actually in contact with a living body when using thebio-electrode, and has electric conductivity and adhesion. The livingbody contact layer is a cured material of the inventive bio-electrodecomposition described above, that is to say, an adherent resin layercomposed of a cured material of a composition containing the component(A), together with the component (B), the component (C), and thecomponent (D) in accordance with needs.

The living body contact layer preferably has adhesion in a range of 0.5N/25 mm or more and 20 N/25 mm or less. The adhesion is commonlymeasured by the method shown in JIS Z 0237, in which a metal substratesuch as a stainless steel (SUS) substrate or a polyethyleneterephthalate (PET) substrate can be used as a base material or,alternatively, human skin can be used for measuring. Human skin haslower surface energy compared to metals and various plastics, which isas low as that of Teflon (registered trade mark), and is hard to adhere.

The living body contact layer of the bio-electrode preferably has athickness of 1 μm or more and 5 mm or less, more preferably 2 μm or moreand 3 mm or less. As the living body contact layer is thinner, theadhesion lowers, but the flexibility is improved, and the weightdecreases to improve the compatibility with skin. The thickness of theliving body contact layer can be selected based on the balance ofadhesion and texture.

The inventive bio-electrode may be provided with an adherent filmseparately on the living body contact layer as previous bio-electrodes(e.g., the bio-electrode described in JP 2004-033468A) in order toprevent peeling off of the bio-electrode from a living body during theuse. When the adherent film is prepared separately, the adherent filmmay be formed by using a raw material for the adherent film such as anacrylic type, a urethane type, and a silicone type. Particularly, thesilicone type is suitable because of the high transparency of oxygen,which enables dermal respiration while pasting the same, the high waterrepellency, which decreases lowering of adhesion due to perspiration,and the low irritation to skin. It is to be noted that the inventivebio-electrode does not necessarily require the adherent film that isprepared separately described above, because peeling off from a livingbody can be prevented by adding tackifier to the bio-electrodecomposition or using a resin having good adhesion to a living body asdescribed above.

When the inventive bio-electrode is used as a wearable device, wiringbetween the bio-electrode and a sensor device, and other components arenot limited to particular ones. For example, it is possible to apply theones described in JP 2004-033468A.

As described above, the inventive bio-electrode is capable of conductingelectric signals from skin efficiently to a device (i.e., excellent inelectric conductivity), free from the risk of causing allergies evenwhen it is worn on skin for a long time (i.e., excellent inbiocompatibility), light-weight, manufacturable at low cost, and freefrom large lowering of the electric conductivity even though it iswetted with water or dried, because the living body contact layer isformed from a cured material of the inventive bio-electrode compositiondescribed above. It is possible to improve the electric conductivitystill more by adding an electro-conductive powder, and to manufacture abio-electrode with higher adhesion and stretchability by combining aresin that has adhesion and stretchability. It is also possible toimprove the stretchability and adhesion to skin using additives, and tocontrol the stretchability and adhesion by adjusting the composition ofthe resin and the thickness of the living body contact layerappropriately. Accordingly, the inventive bio-electrode described aboveis particularly suitable as a bio-electrode used for a medical wearabledevice.

<Method for Manufacturing Bio-Electrode>

The present invention also provides a method for manufacturing abio-electrode having an electro-conductive base material and a livingbody contact layer formed on the electro-conductive base material,comprising: applying the inventive bio-electrode composition describedabove onto the electro-conductive base material; and curing thebio-electrode composition; thereby forming the living body contactlayer.

Incidentally, the electro-conductive base material, etc. used for theinventive method for manufacturing a bio-electrode may be the same asthose described above.

The method for applying the bio-electrode composition onto theelectro-conductive base material is not limited to particular ones; anddip coating, spray coating, spin coating, roll coating, flow coating,doctor coating, screen printing, flexographic printing, gravureprinting, and inkjet printing are suitable, for example.

The method for curing the resin can be appropriately selected based onthe components (A) and (B) used for the bio-electrode compositionwithout being limited to particular methods. For example, thebio-electrode composition is preferably cured by either or both of heatand light. The foregoing bio-electrode composition can also be cured byadding a catalyst to generate acid or base to the bio-electrodecomposition, which causes a crosslinking reaction.

In case of heating, the temperature is not particularly limited and maybe appropriately selected based on the components (A) and (B) used forthe bio-electrode composition, but is preferably about 50 to 250° C.,for example.

When the heating and light irradiation are combined, it is possible toperform the heating and the light irradiation simultaneously, to performthe heating after the light irradiation, or to perform the lightirradiation after the heating. It is also possible to perform air-dryingto evaporate the solvent before heating the coating film.

As described above, the inventive method for manufacturing abio-electrode makes it possible to manufacture the inventivebio-electrode easily and at low cost, with the bio-electrode beingexcellent in electric conductivity and biocompatibility, light-weight,and free from large lowering of the electric conductivity even though itis wetted with water or dried.

EXAMPLE

Hereinafter, the present invention will be specifically described bygiving Examples and Comparative Examples, but the present invention isnot limited thereto. Incidentally, “Me” represents a methyl group, and“Vi” represents a vinyl group.

Each silicone compound bonded to a sulfonimide salt was synthesized bymixing a sulfonimide salt having a double bond, an ether compound havinga double bond in accordance with needs, a silicone compound having anSiH group, and a platinum catalyst in a mixed solvent of toluene andPGMEA in 1:1, followed by heating at 60° C. for 2 hours. After dryingthe solvent, the composition was identified by ¹H-NMR. When the compoundwas a polymer, the weight average molecular weight (Mw) and thedispersity (Mw/Mn) were determined by gel permeation chromatography(GPC) using tetrahydrofuran (THF) as a solvent. Thus synthesizedSulfonimide salt silicones 1 to 7 are shown below.

Sulfonimide Salt Silicone 1

Sulfonimide Salt Silicone 2 Mw=10,800 Mw/Mn=3.22

The repeating number in the formula shows the average value.

Sulfonimide Salt Silicone 3 Mw=10,600 Mw/Mn=2.67

The repeating number in the formula shows the average value.

Sulfonimide Salt Silicone 4 Mw=13,300 Mw/Mn=3.86

The repeating number in the formula shows the average value.

Sulfonimide Salt Silicone 5 Mw=10,800 Mw/Mn=3.88

The repeating number in the formula shows the average value.

Sulfonimide Salt Silicone 6 Mw=13,100 Mw/Mn=3.96

The repeating number in the formula shows the average value.

Sulfonimide Salt Silicone 7 Mw=13,000 Mw/Mn=3.51

The repeating number in the formula shows the average value.

Comparative salts 1 to 4, which were blended as an ionic material to thebio-electrode composition solutions of Comparative Examples, are shownbelow.

Siloxane compounds 1 to 4, which were blended to the bio-electrodecomposition solutions as a silicone base resin, are shown below.

(Siloxane Compound 1)

Siloxane compound 1 was vinyl group-containing polydimethylsiloxanehaving an alkenyl group-content of 0.007 mol/100 g in which theterminals of molecular chain were blocked with SiMe₂Vi groups, with the30% toluene solution having a viscosity of 27,000 mPa·s.

(Siloxane Compound 2)

Siloxane compound 2 was a 60% toluene solution of polysiloxane of MQresin composed of an Me₃SiO_(0.5) unit and an SiO₂ unit (Me₂SiO_(0.5)unit/SiO₂ unit=0.8).

(Siloxane Compound 3)

Siloxane compound 3 was a polydimethylsiloxane-bonded MQ resin obtainedby heating a solution composed of 40 parts by mass of vinylgroup-containing polydimethylsiloxane having an alkenyl group-content of0.007 mol/100 g in which the terminals of molecular chain were blockedwith OH groups, with the 30% toluene solution having a viscosity of42,000 mPa·s; 100 parts by mass of 60% toluene solution of polysiloxaneof MQ resin composed of an Me₂SiO_(0.5) unit and an SiO₂ unit(Me₂SiO_(0.5) unit/SiO₂ unit=0.8); and 26.7 parts by mass of toluenewith refluxing for 4 hours, followed by cooling.

(Siloxane Compound 4)

As methylhydrogensilicone oil, KF-99 manufactured by Shin-Etsu ChemicalCo., Ltd. was used.

As a silicone base resin, KF-353 manufactured by Shin-Etsu Chemical Co.,Ltd. was used, which is polyether type silicone oil with the side chainbeing modified with polyether.

Acrylic polymer blended as an acrylic base resin to the bio-electrodecomposition solution is shown below.

Acrylic Polymer 1 Mw=108,000 Mw/Mn=2.32

The repeating number in the formula shows the average value.

Silicone-urethane acrylates 1 and 2, which were blended to thebio-electrode composition solutions as a silicone base, acrylic base, orurethane base resin, are shown below.

The repeating number in the formula shows the average value.

Organic solvents, which were blended to the bio-electrode compositionsolutions, are shown below.

PGMEA: propylene glycol-1-monomethyl ether-2-acetatePGME: propylene glycol-1-monomethyl etherPGEE: propylene glycol-1-monoethyl ether

The following are metal powders, a radical generator, a platinumcatalyst, and electric conductivity improvers (carbon black and carbonnanotube) blended to the bio-electrode composition solution as anadditive.

Metal Powders:

Silver powder: silver flake manufactured by Sigma-Aldrich Co. LLC., withthe diameter of 10 μm

Gold powder: gold powder manufactured by Sigma-Aldrich Co. LLC., withthe diameter of 10 μm or lessTin powder: tin powder manufactured by Sigma-Aldrich Co. LLC., with thediameter of 45 μm or lessTitanium powder: titanium powder manufactured by Sigma-Aldrich Co. LLC.,with the diameter of 45 μm or lessCopper powder: copper powder manufactured by Sigma-Aldrich Co. LLC.,with the diameter of 45 μm or lessRadical generator: V-601 manufactured by FUJI FILM Wako Pure ChemicalCorporationPlatinum catalyst: CAT-PL-50T manufactured by Shin-Etsu Chemical Co.,Ltd.Carbon black: DENKA BLACK HS-100 manufactured by Denka Co., Ltd.Multilayer carbon nanotube: manufactured by Sigma-Aldrich Co. LLC., withthe diameter of 110 to 170 nm and the length of 5 to 9 μm

Examples 1 to 17, Comparative Examples 1 to 5

On the basis of each composition described in Table 1 and Table 2, theionic material (Sulfonimide salt silicone, Comparative salt), the resin,the organic solvent, and the other additives (radical generator,platinum catalyst, electric conductivity improver) were blended toprepare each bio-electrode composition solution (Bio-electrodecomposition solutions 1 to 17, Comparative bio-electrode compositionsolutions 1 to 5).

TABLE 1 Bio-electrode Ionic Organic composition material Resins solventAdditives solution (parts by mass) (parts by mass) (parts by mass)(parts by mass) Bio-electrode Sulfonimide Siloxane compound 1 (40)toluene CAT-PL-50T (1.5) composition salt silicone Siloxane compound 2(90) (30) Carbon black solution 1 1 (10) KF-99 (3) (10) KF-353 (10)Bio-electrode Sulfonimide Siloxane compound 3 (126) heptane CAT-PL-50T(0.7) composition salt silicone KF-99 (3) (30) Carbon black solution 2 2(20) KF-353 (5) PGMEA (14) (10) Bio-electrode Sulfonimide Siloxanecompound 1 (40) toluene CAT-PL-50T (0.7) composition salt siliconeSiloxane compound 2 (100) (30) Carbon black solution 3 3 (20) KF-99 (3)PGMEA (14) (10) Bio-electrode Sulfonimide Siloxane compound 1 (40)toluene CAT-PL-50T (0.7) composition salt silicone Siloxane compound 2(100) (30) Carbon black solution 4 4 (18) KF-353 (8) PGMEA (14) (10)Bio-electrode Sulfonimide Siloxane compound 3 (126) toluene CAT-PL-50T(1.0) composition salt silicone KF-353 (10) (44) Carbon black solution 55 (20) (10) Bio-electrode Sulfonimide Siloxane compound 1 (40) toluene(30) CAT-PL-50T (2.0) composition salt silicone Siloxane compound 2(100) 2-heptanone Carbon black solution 6 6 (20) KF-99 (3) (14) (10)Bio-electrode Sulfonimide Siloxane compound 1 (40) toluene (30)CAT-PL-50T (2.0) composition salt silicone Siloxane compound 2 (100)2-heptanone Carbon black solution 7 7 (20) KF-99 (3) (14) (10)Bio-electrode Sulfonimide Siloxane compound 1 (40) toluene CAT-PL-50T(1.5) composition salt silicone Siloxane compound 2 (100) (30) Silverpowder (5) solution 8 6 (20) KF-99 (3) PGME (14) Carbon black (5)Bio-electrode Sulfonimide Siloxane compound 1 (40) toluene CAT-PL-50T(1.5) composition salt silicone Siloxane compound 2 (100) (30) Silverpowder (5) solution 9 6 (20) KF-99 (3) PGEE (14) Multilayer carbonnanotube (3) Bio-electrode Sulfonimide Acrylic polymer 1 (60) PGMEA(100) Radical generator composition salt silicone Silicone-urethaneV-601 (4) solution 10 3 (20) acrylate 1 (20) Silver powder (10)Bio-electrode Sulfonimide Acrylic polymer 1 (55) PGMEA (100) Radicalgenerator composition salt silicone Silicone-urethane V-601 (4) solution11 3 (20) acrylate 1 (25) Gold powder (10) Bio-electrode SulfonimideAcrylic polymer 1 (60) PGMEA (100) Radical generator composition saltsilicone Silicone-urethane V-601 (4) solution 12 3 (20) acrylate 2 (20)Silver powder (10) Bio-electrode Sulfonimide Siloxane compound 1 (40)toluene CAT-PL-50T (1.5) composition salt silicone Siloxane compound 2(100) (30) Tin powder (10) solution 13 6 (20) KF-353 (26) PGEE (14)Bio-electrode Sulfonimide Siloxane compound 1 (40) toluene (30)CAT-PL-50T (1.5) composition salt silicone Siloxane compound 2 (100)cyclopentanone Tin powder (5) solution 14 6 (20) KF-353 (26) (14) Carbonblack (5) Bio-electrode Sulfonimide Siloxane compound 1 (40) toluene(30) CAT-PL-50T (1.5) composition salt silicone Siloxane compound 2(100) cyclopentanone Titanium powder solution 15 6 (20) KF-353 (26) (14)(10) Bio-electrode Sulfonimide Siloxane compound 1 (40) toluene (30)CAT-PL-50T (1.5) composition salt silicone Siloxane compound 2 (100)cyclopentanone Titanium powder (5) solution 16 6 (20) KF-353 (26) (14)Carbon black (5) Bio-electrode Sulfonimide Siloxane compound 1 (40)toluene (30) CAT-PL-50T (1.5) composition salt silicone Siloxanecompound 2 (100) cyclopentanone Copper powder solution 17 6 (20) KF-353(26) (14) (10)

TABLE 2 Bio-electrode Ionic Organic composition material Resins solventAdditives solution (parts by mass) (parts by mass) (parts by mass)(parts by mass) Comparative Comparative Siloxane compound 3 (126)toluene (30) CAT-PL-50T (1.5) bio-electrode salt 1 KF-99 (2.5) PGME (14)Carbon black composition (4.7) KF-353 (10) (10) solution 1 ComparativeComparative Siloxane compound 3 (126) toluene (30) CAT-PL-50T (1.5)bio-electrode salt 2 KF-99 (2.5) PGME (14) Carbon black composition(8.2) KF-353 (10) (10) solution 2 Comparative Comparative Siloxanecompound 3 (126) toluene (30) CAT-PL-50T (1.5) bio-electrode salt 3KF-99 (2.5) PGME (14) Carbon black composition (8.4) KF-353 (10) (10)solution 3 Comparative Comparative Siloxane compound 3 (126) toluene(30) CAT-PL-50T (1.5) bio-electrode salt 4 KF-99 (2.5) PGME (14) Carbonblack composition (8.4) KF-353 (10) (10) solution 4 Comparative —Siloxane compound 3 (126) toluene (30) CAT-PL-50T (1.5) bio-electrodeKF-99 (2.5) PGME (14) Carbon black composition KF-353 (10) (10) solution5

(Evaluation of Electric Conductivity)

Each bio-electrode composition solution was applied onto an aluminumdisk having a diameter of 3 cm and a thickness of 0.2 mm by using anapplicator. This was air-dried at room temperature for 6 hours and thenbaked at 120° C. for 30 minutes under a nitrogen atmosphere by using anoven to be cured, thereby producing four pieces of bio-electrodes foreach bio-electrode composition solution. Thus obtained bio-electrode hadthe living body contact layer 3 at one side and the aluminum disk 8 atthe other side as an electro-conductive base material as shown in FIGS.3A and 3B. Then, the copper wiring 9 was pasted on the surface of thealuminum disk 8 with self-adhesive tape at the side that had not beencoated with the living body contact layer to form a lead-out electrode,which was connected to an impedance measurement apparatus as shown inFIG. 3B. Two pieces of the bio-electrodes 1′ were pasted on a human armat a distance of 15 cm from each other such that the side of each livingbody contact layer was in contact with the skin of the human arm asshown in FIG. 4. The initial impedance was measured while altering thefrequency by using an AC impedance measurement apparatus SI1260manufactured by Solartron. Then, the remained two pieces of thebio-electrodes were immersed in pure water for 1 hour, and used formeasuring the impedance on skin by the same method described above afterdrying the water. Each impedance at the frequency of 1,000 Hz is shownin Table 3.

(Evaluation of Adhesion)

Each bio-electrode composition solution was applied onto a polyethylenenaphthalate (PEN) substrate having a thickness of 100 μm by using anapplicator. This was air dried at room temperature for 6 hours, followedby curing through baking at 120° C. for 30 minutes under a nitrogenatmosphere by using an oven to produce an adhesive film. From thisadhesive film, a tape with a width of 25 mm was cut out. This waspressed to a stainless (SUS304) board and allowed to stand at roomtemperature for 20 hours. Then, the force (N/25 mm) for peeling thetape, which had been produced from the adhesive film, from the stainlessboard was measured at an angle of 180° and a speed of 300 ram/min byusing a tensile tester. The results are shown in Table 3.

(Measurement of Thickness of Living Body Contact Layer)

On each bio-electrode produced in the evaluation test of electricconductivity described above, the thickness of the living body contactlayer was measured by using a micrometer. The results are shown in Table3.

TABLE 3 Thickness Impedance of Initial after Bio-electrode Adhesionresin impedance water immersion Example composition solution (N/25 mm)(μm) (Ω) (Ω) Example 1 Bio-electrode 3.1 480 9.3 E⁴ 8.9 E⁴ compositionsolution 1 Example 2 Bio-electrode 3.8 390 4.3 E⁴ 5.1 E⁴ compositionsolution 2 Example 3 Bio-electrode 3.5 540 7.5 E⁴ 7.9 E⁴ compositionsolution 3 Example 4 Bio-electrode 3.7 590 3.1 E⁴ 3.2 E⁴ compositionsolution 4 Example 5 Bio-electrode 3.8 580 3.9 E⁴ 4.3 E⁴ compositionsolution 5 Example 6 Bio-electrode 3.9 550 3.5 E⁴ 4.1 E⁴ compositionsolution 6 Example 7 Bio-electrode 3.6 530 3.9 E⁴ 3.8 E⁴ compositionsolution 7 Example 8 Bio-electrode 3.1 660 3.5 E⁴ 3.8 E⁴ compositionsolution 8 Example 9 Bio-electrode 4.2 490 4.2 E⁴ 4.6 E⁴ compositionsolution 9 Example 10 Bio-electrode 2.3 460 5.2 E⁴ 5.9 E⁴ compositionsolution 10 Example 11 Bio-electrode 2.1 570 9.4 E⁴ 9.8 E⁴ compositionsolution 11 Example 12 Bio-electrode 2.1 560 8.1 E⁴ 8.6 E⁴ compositionsolution 12 Example 13 Bio-electrode 3.3 470 9.6 E⁴ 9.4 E⁴ compositionsolution 13 Example 14 Bio-electrode 3.1 460 8.5 E⁴ 9.1 E⁴ compositionsolution 14 Example 15 Bio-electrode 3.1 510 8.1 E⁴ 7.9 E⁴ compositionsolution 15 Example 16 Bio-electrode 3.0 390 7.1 E⁴ 7.8 E⁴ compositionsolution 16 Example 17 Bio-electrode 3.2 380 9.1 E⁴ 9.1 E⁴ compositionsolution 17 Comparative Comparative bio-electrode 3.3 520 4.2 E⁴ 5.3 E⁵Example 1 composition solution 1 Comparative Comparative bio-electrode3.2 530 8.2 E⁴ 7.3 E⁵ Example 2 composition solution 2 ComparativeComparative bio-electrode 3.6 520 7.1 E⁴ 9.3 E⁵ Example 3 compositionsolution 3 Comparative Comparative bio-electrode 3.6 560 1.1 E⁵ 1.1 E⁶Example 4 composition solution 4 Comparative Comparative bio-electrode3.9 530 1.9 E⁷ 2.8 E⁷ Example 5 composition solution 5

As shown in Table 3, in each of Examples 1 to 17, the living bodycontact layer of which was formed by using the inventive bio-electrodecomposition containing a sulfonimide salt silicone compound and resins,the initial impedance was low, and the impedance did not cause largechange after the bio-electrodes were immersed to water and dried. Thatis, Examples 1 to 17 each gave a bio-electrode that had high initialelectric conductivity and did not cause large lowering of the electricconductivity even though it was wetted with water or dried. Thesebio-electrodes of Examples 1 to 17 had good adhesion similar to that ofbio-electrode of Comparative Examples 1 to 5, in which previous salt andresin were blended, and was light-weight, excellent in biocompatibility,and manufacturable at low cost.

On the other hand, in each Comparative Examples 1 to 4, the living bodycontact layer of which was formed by using a bio-electrode compositioncontaining previous salt and resins, the initial impedance was low, butlarge increase of the impedance occurred such that the order ofmagnitude was changed after water immersion and drying. That is, each ofComparative Examples 1 to 4 only gave a bio-electrode, the electricconductivity of which was largely decreased when it was wetted by waterand dried, although the initial electric conductivity was high.

Comparative Example 5, in which the living body contact layer was formedby using a bio-electrode composition that contained resins withoutcontaining salt, did not cause large increase of impedance by an orderof magnitude after it was immersed to water and dried because it did notcontain salt, but the initial impedance was high. That is, ComparativeExample 5 only gave a bio-electrode with low initial electricconductivity.

As described above, it was revealed that the bio-electrode, with theliving body contact layer being formed by using the inventivebio-electrode composition, was excellent in electric conductivity,biocompatibility, and adhesion to an electro-conductive base material;excellent in holding the ionic material to prevent large lowering ofelectric conductivity even though it was wetted with water or dried;light-weight; and manufacturable at low cost.

It is to be noted that the present invention is not restricted to theforegoing embodiment. The embodiment is just an exemplification, and anyexamples that have substantially the same feature and demonstrate thesame functions and effects as those in the technical concept describedin claims of the present invention are included in the technical scopeof the present invention.

1. A bio-electrode composition comprising a silicone bonded to asulfonimide salt, wherein the sulfonimide salt is shown by the followinggeneral formula (1):

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms or an arylene group having 6 to 10 carbonatoms, with the alkylene group optionally having an aromatic group, anether group, or an ester group; Rf represents a linear, branched, orcyclic alkyl group having 1 to 4 carbon atoms and containing at leastone fluorine atom; M⁺ is an ion selected from a lithium ion, a sodiumion, a potassium ion, and a silver ion.
 2. The bio-electrode compositionaccording to claim 1, wherein the silicone bonded to a sulfonimide salthas a repeating unit-a shown by the following general formula (2):

wherein R¹, Rf, and M⁺ are as defined above; R² represents a linear,branched, or cyclic alkyl group having 1 to 10 carbon atoms or an arylgroup having 6 to 10 carbon atoms, with the alkyl group optionallysubstituted by a halogen atom.
 3. The bio-electrode compositionaccording to claim 1, further comprising an adhesive resin as acomponent (B) in addition to the silicone bonded to a sulfonimide saltas a component (A).
 4. The bio-electrode composition according to claim2, further comprising an adhesive resin as a component (B) in additionto the silicone bonded to a sulfonimide salt as a component (A).
 5. Thebio-electrode composition according to claim 3, wherein the component(B) is one or more resins selected from a silicone resin, a(meth)acrylate resin, and a urethane resin.
 6. The bio-electrodecomposition according to claim 4, wherein the component (B) is one ormore resins selected from a silicone resin, a (meth)acrylate resin, anda urethane resin.
 7. The bio-electrode composition according to claim 3,wherein the component (B) contains a silicone resin having anR_(x)SiO_((4-x)/2) unit (wherein, R represents a substituted orunsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms,and “x” is a number in a range of 2.5 to 3.5) and an SiO₂ unit,diorganosiloxane having an alkenyl group, and organohydrogenpolysiloxanehaving an SiH group.
 8. The bio-electrode composition according to claim4, wherein the component (B) contains a silicone resin having anR_(x)SiO_((4-x)/2) unit (wherein, R represents a substituted orunsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms,and “x” is a number in a range of 2.5 to 3.5) and an SiO₂ unit,diorganosiloxane having an alkenyl group, and organohydrogenpolysiloxanehaving an SiH group.
 9. The bio-electrode composition according to claim5, wherein the component (B) contains a silicone resin having anR_(x)SiO_((4-x)/2) unit (wherein, R represents a substituted orunsubstituted monovalent hydrocarbon group having 1 to 10 carbon atoms,and “x” is a number in a range of 2.5 to 3.5) and an SiO₂ unit,diorganosiloxane having an alkenyl group, and organohydrogenpolysiloxanehaving an SiH group.
 10. The bio-electrode composition according toclaim 1, further comprising a carbon powder and/or a metal powder as acomponent (C).
 11. The bio-electrode composition according to claim 10,wherein the carbon powder is either or both of carbon black and carbonnanotube.
 12. The bio-electrode composition according to claim 11,wherein the metal powder is a powder of a metal selected from gold,silver, platinum, copper, tin, titanium, nickel, aluminum, tungsten,molybdenum, ruthenium, chromium, and indium.
 13. The bio-electrodecomposition according to claim 12, wherein the metal powder is a silverpowder, a copper powder, a tin powder, or a titanium powder.
 14. Thebio-electrode composition according to claim 1, further comprising anorganic solvent as a component (D).
 15. A bio-electrode comprising anelectro-conductive base material and a living body contact layer formedon the electro-conductive base material; wherein the living body contactlayer is a cured material of the bio-electrode composition according toclaim
 1. 16. The bio-electrode according to claim 15, wherein theelectro-conductive base material comprises one or more species selectedfrom gold, silver, silver chloride, platinum, aluminum, magnesium, tin,tungsten, iron, copper, nickel, stainless steel, chromium, titanium,carbon, and an electro-conductive polymer.
 17. A method formanufacturing a bio-electrode having an electro-conductive base materialand a living body contact layer formed on the electro-conductive basematerial, comprising: applying the bio-electrode composition accordingto claim 1 onto the electro-conductive base material; and curing thebio-electrode composition; thereby forming the living body contactlayer.
 18. The method for manufacturing a bio-electrode according toclaim 17, wherein the electro-conductive base material comprises one ormore species selected from gold, silver, silver chloride, platinum,aluminum, magnesium, tin, tungsten, iron, copper, nickel, stainlesssteel, chromium, titanium, carbon, and an electro-conductive polymer.19. A silicone compound comprising a partial structure shown by thefollowing general formula (2):

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms or an arylene group having 6 to 10 carbonatoms, with the alkylene group optionally having an aromatic group, anether group, or an ester group; R² represents a linear, branched, orcyclic alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 10 carbon atoms, with the alkyl group optionally substituted by ahalogen atom; Rf represents a linear, branched, or cyclic alkyl grouphaving 1 to 4 carbon atoms and containing at least one fluorine atom; M⁺is an ion selected from a lithium ion, a sodium ion, a potassium ion,and a silver ion.
 20. A silicone polymer comprising a repeating unitshown by the following general formula (2), and having a weight averagemolecular weight in a range of 1000 to 1000000,

wherein R¹ represents a linear, branched, or cyclic alkylene grouphaving 1 to 20 carbon atoms or an arylene group having 6 to 10 carbonatoms, with the alkylene group optionally having an aromatic group, anether group, or an ester group; R² represents a linear, branched, orcyclic alkyl group having 1 to 10 carbon atoms or an aryl group having 6to 10 carbon atoms, with the alkyl group optionally substituted by ahalogen atom; Rf represents a linear, branched, or cyclic alkyl grouphaving 1 to 4 carbon atoms and containing at least one fluorine atom; M⁺is an ion selected from a lithium ion, a sodium ion, a potassium ion,and a silver ion.